| args {base} | R Documentation |
Argument List of a Function
Description
Displays the argument names and corresponding default values of a (non-primitive or primitive) function.
Usage
args(name)
Arguments
name |
a function (a primitive or a closure, i.e.,
“non-primitive”).
If |
Details
This function is mainly used interactively to print the argument list
of a function. For programming, consider using formals
instead.
Value
For a closure, a closure with identical formal argument list but an
empty (NULL) body.
For a primitive (function), a closure with the documented usage and NULL
body. Note that some primitives do not make use of named arguments
and match by position rather than name.
NULL in case of a non-function.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
See Also
formals, help;
str also prints the argument list of a function.
Examples
## "regular" (non-primitive) functions "print their arguments"
## (by returning another function with NULL body which you also see):
args(ls)
args(graphics::plot.default)
utils::str(ls) # (just "prints": does not show a NULL)
## You can also pass a string naming a function.
args("scan")
## ...but :: package specification doesn't work in this case.
tryCatch(args("graphics::plot.default"), error = print)
## As explained above, args() gives a function with empty body:
list(is.f = is.function(args(scan)), body = body(args(scan)))
## Primitive functions mostly behave like non-primitive functions.
args(c)
args(`+`)
## primitive functions without well-defined argument list return NULL:
args(`if`)